Gaseous electric discharge device



Nov. s, 1938. I R WALK-ER 2,135,776

GASEOUS ELECTRIC DISCHARGE DEVICE Original Filed Dec. 13, 1932.

Fig.5

Allllla I INVENTOR Warren R. We: I ker ATTORNEY Patented Nov. 8, 1 938 I GASEOUS ELECTRIC DISCHARGE DEVICE Warren R. Walker, Short Hills, N. 1., asslgnor to General Electric Vapor Lamp Company, Hoboken, N. J., a corporation of New Jersey Original application December 13, 1932, Serial No. 647,016, now Patent No. 2,076,755, dated April 13, 1937.

Divided .and this application January 21, 1937, Serial No. 121,504

1 'Claim. (Cl. 176-45) The present invention relates to electric discharge devices, and particularly to apparatus for.

starting and operating the same.

. A particular object of the invention is to provide apparatus which will be extremely effective to start gas or vapor discharge devices into operation. Another object of the invention is to provide apparatus which will limit the potentials which are applied to initiate the discharge. Other'objects and advantages of the invention will appear from the following detailed specification or from an inspection of the accompanying drawing.

The invention consists in the new and novel apparatus hereinafter set forth and claimed.

The starting of electric gaseous discharge devices, and particularly of those devices having liquid cathodes, such as mercury vapor arcs, has

' long been an especially troublesome problem.

High frequency alone is insuflicient to initiate an arc discharge to a mercury cathode, it having beenfound that it is necessary to provide enough energy to produce a-hot spot on the cathode before the arc can be started. For example, 2. voltage surge, produced by interrupting the flow of current through an inductance by means of a mercury switch, has heretofore been used for the purpose of starting an arc in a mercury vapor arc lamp. I'have now discovered, however, that by using a switch having solid contacts operating in a vacuum to interrupt the current flow through this inductance a new type of discharge is produced which is many more times more effective in starting the main arc than was the simple surge heretofore used. This discharge is not only of greater potential, for a given current and inductance, due'to the more rapid interruption of the circuit in my novel switch, but also gives indications of having an extremely high frequency. This unique combination of high energy and high frequency is the ideal forstarting a mercury vapor arc, since it not only produces the necessary hot spot, but also effectively initiates the main arc thereto. As a result instantaneous starting of the mercury arc, an ideal long sought, is now consistently attained for the first time. In some cases it is desirable to place a limitation on the potential which is produced by'thisapparatus, however, in order to safeguard the insulation and the like. I have found that such a limitation is attained by placinga spark gap across the terminals of the switch. i

For the purpose of illustrating my invention I have shown several embodiments thereof in the accompanying drawing, in which Fig. 1 is a schematic diagram showing my novel combination of a mercury arc lamp with a vac-' uum switch, and

Fig. 2 is an elevational view, in part section, of the novel switch which I prefer to use-in my new combination.

In the drawing, with particular reference to Fig. 1, there is shown a mercury vapor arc lamp I of the well known Cooper-Hewitt type having a mercury cathode 2, starting band 3,'and anodes 4. Said anodes l are each connected in a conventional manner through a ballast resistance 5 to opposite ends of an autotransformer 6. The

midpoint of said autotransformer is connected through an inductance l to said cathode 2. From a point between said inductance and said cathode a connection is made through the vacuum switch 8, which is actuated by said inductance I, and a resistance 9 to one of the anode leads. The starting band 3 is connected to a point between sai switch 8 and said resistance 9.

Said switch 8 is shown in detail in Fig. 2. This novel switch, which is claimed in my Patent 1,984,505, granted December 18, 1934, consists of a sealed vitreous envelope I I which is highly evacuated. A pair of inleads 12 extend through opposite ends of said envelope, a horizontal contact plate l3 which extends from wallto wall of said envelope being welded to the inner end of each of said inleads. A hubbed disc H of porcelain or the like is mounted on each inlead between said contact plate and the seal and is freely rotatable on said inlead. Said discs serve as stops for the endwise movement of a bridging conductor l5 which is supported on the contact plates l3. Said bridging conductor I5 is tubular, and may conveniently be formed of tungsten wire wound into a tight helix. Within said bridging member there is'retained in any suitable mannera rod iii of magnetizable material, such as iron. Said rodhas a diameter which is appreciably less than the inner diameter of said tubular bridging member and hence has considerable freedom of movement therein In the use and operation of the foregoing apparatus, upon energization of the autotransformer 6, potential is applied between the anodes 4 andv the cathode 2, but this potential is insuflicient to initiate a discharge. Current flows, however, from one end of said autotransformer through the resistance 9, switch 8, and inductance I back to the midpoint of said autotransformer. As soongas said inductance I is thus energized the iron rod I6 is raised and strikes a hammer blow on the surrounding bridging member I5. This hammer blow, plus the turning moment exerted by the pull on the free end of said bridging member, is sufllcient to free said bridging member even though it is frozen or partially welded fast at one end, as frequently occurs, and hence this bridging member is immediately raised to the top of the envelope II, and the circuit through said switch 8 is opened.- Said inductance I thereupon generates a voltage surge or discharge, as a result of which said cathode 2 is momentarily made intensely negative with respect -to the anodes 4 and the starting band 3. A disruptive discharge thereupon occurs at said cathode which produces a. hot spot on the mercury cathode and suflicient ionization in the arc tube to permit the main arc to start from the anodes 4. The nature of the surge or discharge generated by this novel combination of the inductance I and the switch 8 is unique, in that it has a high frequency component which remarkably assists in the initiation of the desired arc, it having been found that with this novel combination of elements a mercury vapor arc lamp can now be started with the same certainty and despatch as an incandescent lamp, an ideal which'has been unattainable heretofore.

Where it is desired to limit the maximum po-.

tential to some given value, in order to safeguard the insulation and to prevent undesirable arcing between leads, a spark gap I1 is connected across the terminals of the switch I. This spark gap may be of any desired type, but as here shown the.

The unique characteristics of the voltage surge produced by this combination provide a startling improvement in the starting of this type of device, which permits the starting to be produced with great certainty and celerity, even at very low temperatures atwhich the apparatus heretofore.

employed has been ineffective, while at the same time the spark gap employed aflords protection against occasional surges of excessive value.

While I have described my invention by reference to particular embodiments thereof, it is to be understood that various changes; omissions and substitutions, within the scope of the appended claim, may be made therein without dedevice, means to initiate a discharge therein comprising-an inductance connected to one of the electrodes of said device. and means to connect said inductance to a source of energy through an evacuated metal to metal contact switch, said switch being responsive to current flow through said inductance to open said circuit and thereby impress a voltage surge on said device, and a spark gap in parallel with said switch, the breakdown potential of said spark gap being considerably in excess of the sparking potential oi: said switch but below the potential at which an areover can occur between the leads to said switch, whereby the ,surges produced by cooperation oi. said switch and said inductance are impressed on said device without reduction except when the peak voltage thereof exceeds said breakdown potential.

WARREN R.-WALKER. 

